How to Build Your Own Worm Composter

If you're interested in constructing a home for your composting worms instead of buying one, you can start with this simple double-decker design, which includes a built-in method for harvesting vermicompost. If you prefer to get your feet wet with just one bin, follow the basic drilling instructions for the double-decker bin, substituting one bin. (You still need two lids: one for a lid and one for a drip tray.)

Using the 1/4-inch (6.35 millimeter) drill bit, make 20 holes evenly spaced in the bottom of each bin.

These holes allow drainage so conditions won't become too wet, and they promote aeration, which is essential to an aerobic composting environment. When it's time to harvest castings, your worms will travel through the holes from one bin into the other (see Step 5.)

Using the 1/16-inch (1.58 millimeter) bit, drill smaller aeration holes every 1 to 2 inches (2.5 to 5 centimeters) on each side of each bin near the top edge.

Using the 1/16-inch (1.58 millimeter) bit, drill about 30 small holes in the top of one of the lids to allow for aeration.

Leave the second lid without holes to act as a tray to catch drips.

Set the drip tray on the floor. Position the two bricks on the tray to provide good balance when one full bin is set on top.

Raising the worm bin several inches off the floor with bricks promotes air flow beneath it.

You do all your vermicomposting in this bottom bin. When it's time to harvest the compost, pull out the top bin and follow these steps:

Place fresh, moist bedding in the second, empty bin.

Remove the lid from the first (bottom) bin and set the fresh bin directly on the vermicompost surface. Put the lid on the fresh bin.

Bury all new food scraps in the fresh bin.

Most worms will gradually relocate to the fresh bin (through the holes in the bottom) in search of food. It could take two to four weeks (or longer) for most of them to move to the new bin.

After most of the worms have made the move, harvest your vermicompost from the first bin.

If you use only a single bin, the same principle applies: Worms head for the chow line, so put food scraps on one side of the bin. After they've traveled to that side, harvest the vacated vermicompost on the other, and then repeat the process on the other side.